Refactor recording of the Startup.FirstWebContents.RenderProcessHostInit.ToNonEmptyPaint metric

components/startup_metric_utils/browser/startup_metric_utils.cc

Index: components/startup_metric_utils/browser/startup_metric_utils.cc
diff --git a/components/startup_metric_utils/browser/startup_metric_utils.cc b/components/startup_metric_utils/browser/startup_metric_utils.cc
index f55f8907e00648b8e67d50e8d134959d2de385db..c60640f6dac1c81e27cccef20839e497b23e526a 100644
--- a/components/startup_metric_utils/browser/startup_metric_utils.cc
+++ b/components/startup_metric_utils/browser/startup_metric_utils.cc
@@ -47,6 +47,9 @@ base::LazyInstance<base::TimeTicks>::Leaky g_process_creation_ticks =
 base::LazyInstance<base::TimeTicks>::Leaky g_browser_main_entry_point_ticks =
     LAZY_INSTANCE_INITIALIZER;
 
+base::LazyInstance<base::TimeTicks>::Leaky
+    g_first_render_process_host_init_ticks = LAZY_INSTANCE_INITIALIZER;
+
 base::LazyInstance<base::TimeTicks>::Leaky g_renderer_main_entry_point_ticks =
     LAZY_INSTANCE_INITIALIZER;
 
@@ -698,6 +701,11 @@ void RecordBrowserOpenTabsDelta(base::TimeDelta delta) {
       UMA_HISTOGRAM_LONG_TIMES_100, "Startup.BrowserOpenTabs", delta);
 }
 
+void RecordFirstRenderProcessHostInit(base::TimeTicks ticks) {
+  if (g_first_render_process_host_init_ticks.Get().is_null())
+    g_first_render_process_host_init_ticks.Get() = ticks;
+}
+
 void RecordRendererMainEntryTime(base::TimeTicks ticks) {
   // Record the renderer main entry time, but don't log the UMA metric
   // immediately because the startup temperature is not known yet.
@@ -718,11 +726,9 @@ void RecordFirstWebContentsMainFrameLoad(base::TimeTicks ticks) {
       g_process_creation_ticks.Get(), ticks);
 }
 
-void RecordFirstWebContentsNonEmptyPaint(
-    base::TimeTicks now,
-    base::TimeTicks render_process_host_init_time) {
+void RecordFirstWebContentsNonEmptyPaint(base::TimeTicks ticks) {
   static bool is_first_call = true;
-  if (!is_first_call || now.is_null())
+  if (!is_first_call || ticks.is_null())
     return;
   is_first_call = false;
 
@@ -737,16 +743,16 @@ void RecordFirstWebContentsNonEmptyPaint(
       metrics::CallStackProfileMetricsProvider::FIRST_NONEMPTY_PAINT);
   UMA_HISTOGRAM_AND_TRACE_WITH_TEMPERATURE_AND_SAME_VERSION_COUNT(
       UMA_HISTOGRAM_LONG_TIMES_100, "Startup.FirstWebContents.NonEmptyPaint2",
-      g_process_creation_ticks.Get(), now);
+      g_process_creation_ticks.Get(), ticks);
   UMA_HISTOGRAM_WITH_TEMPERATURE(
       UMA_HISTOGRAM_LONG_TIMES_100,
       "Startup.BrowserMessageLoopStart.To.NonEmptyPaint2",
-      now - g_message_loop_start_ticks.Get());
+      ticks - g_message_loop_start_ticks.Get());
 
-  UMA_HISTOGRAM_WITH_TEMPERATURE(
+  UMA_HISTOGRAM_AND_TRACE_WITH_TEMPERATURE_AND_SAME_VERSION_COUNT(

[gab, 2017/06/02 18:31:33]

Let's not bother with "AND_SAME_VERSION_COUNT" (we should drop that suffix, no
one looks at it anymore IMO)

       UMA_HISTOGRAM_LONG_TIMES_100,
       "Startup.FirstWebContents.RenderProcessHostInit.ToNonEmptyPaint",
-      now - render_process_host_init_time);
+      g_first_render_process_host_init_ticks.Get(), ticks);
 }
 
 void RecordFirstWebContentsMainNavigationStart(base::TimeTicks ticks,